Recent Posts

Welcome to the new TRS website – a one-stop-shop for anyone interested in studying UK tachinid flies. The site has the very latest news & information from the recording scheme plus the most up to date species list and key updates.

Currently the Species Accounts page allows you to search for anything on the British list; view the data we hold on it, including excerpts from all of the major works; view any photos we have of specimens or insects in the field; and also to link to the NBN mapping database, which currently hold 15,000 of our recording scheme records plus records from other regional and national recording projects.

Recently I have been working on adding a new species to the British list to our key. Thelyconychia solivaga is a small tachinid that seems to live on fairly stony/rocky coastal sites and is very rare in the UK – in fact only 3 specimens have been found so far (by Laurence Clemons in Kent and Ivan Perry in Sussuex). These are just a few photos to show how it looks but it is a rather nondescript species that looks superficially like a small Meigenia but the apicals are crossed and the propleuron is not hairy.

They are actually so rarely collected that the Natural History Museum has 6 specimens – mostly collected in Jordan!

The genus Phryxe contains a few common species (nemea, vulgaris & heraclei) and a few very rare ones (magnicornis & erythrostoma). The key pulls out nemea first by the wide gap between the facial-ridge bristles and the descending parafrontals – wider than the width of antenna-3 plus the mustardy/yellow frontal area. Splitting off heraclei has always been a matter of looking for extra bristles along the underside of costal wing section 2, which indicate heraclei – without this would mean moving on to magnicornis (split off using male genitalia), erythrostoma (big with long claws) & vulgaris (the rest). So it’s clear that male genitalia are important (once you get past nemea) but recently I have found several specimens that have vulgaris-type genitalia but which have the extra bristlets along wing section 2.

The first pair of photos shows a standard male Phryxe heraclei – the wing edge section has a scattering of extra bristlets on the underside of the vein between the leading edge and the wing membrane. The genitalia have very rounded surstyli and a smoothly rounded cercus:

The next photo shows the troublesome Phryxe vulgaris – the wing edge also has stray bristlets and the genitalia are of the usual vulgaris/nemea type with more elongate surstyli and a more angled cercus:

This means that once nemea has been excluded you really need to have a male specimen to prove vulgaris, magnicornis or heraclei. Phryxe erythrostoma is much larger and the claws are also quite distinctive. So, in summary:

Female specimens:

1. The gap between the descending parafrontal bristles and the ascending facial ridge bristles is about as wide as the width of antenna-3 and the colour of the parafrontal region is a yellowish-grey … Phryxe nemea

– The gap narrower and the colour of the parafrontal dusting is more a blue-grey … other species

Male specimens: (continuing from above):

2. surstyli rounded and cerci smoothly curved underneath; underside of costal section 2 with 1 or more additional tiny bristlets along the vein between the continuous row of bristlets on the leading edge and the wing membrane … Phryxe heraclei

5. surstylus moderately elongate – between that of heraclei and magnicornis (as above) and cercus with a distinct angle to the underside … Phryxe vulgaris

In reality if you have a male and the genitalia look like nemea/vulgaris type then you just have to decide which species it is from the facial bristle gap and the colour of the dusting – you don’t have to progress to the other species.

In the keys to Gonia one of the couplets asks you to consider the shininess of the face but this can be a confusing thing to judge when you only have one specimen. In this mini article I have taken photos of the 2 choices to make it clear. The first thing to do is to make sure that you are looking from the front with even light.

The first photo shows Gonia capitata (but also ornata looks like this) and these are the species described as “reflective yellowish-white” while the last photo shows Gonia divisa, which is the species described as “matt orange”. Really both species have an orange face but capitata/ornata are highly dusted with reflective scales while divisa is not shiny..

For many years Linnaemya picta had been confused with rossica because early workers (e.g. Fonseca) hadn’t tried using the European keys. Since the ‘discovery’ of picta in Kent it has spread across southern England as far as Bedfordshire, Oxfordshire & Berkshire and so now we have another fairly common black-legged species to confuse with tessellans. I have occasionally been confused myself by 2 couplets in the Linnaemya keys and so I have posted here some photos of the various species and illustrated the features that you need to look out for.

Firstly, both picta & tessellans have dark hairs on the gena but picta has bristles mixed in with them. The bristles should be fairly obvious because they arise from sockets, while the hairs go directly into the integument.

Secondly, both picta & rossica have a scattering of small black bristlets on top of the head, behind the post-ocular row. But rossica is distinctive in having many more bristles in multiple rows and at least a few of them are as large as medium-sized post-ocular bristles. This feature is actually very easy to find but can cause confusion if you only have a picta and don’t know whether your bristles are big enough.

Linnaemya picta showing bristles on the gena

Linnaemya tessellans showing just hairs on the gena

Linnaemya picta showing a few small bristlets on the top of the head behind the post ocular row

Linnaemya rossica showing many more black bristlets and a few much larger ones behind the post-ocular row

In Andersen’s 1996 book “The Siphonini (Diptera: Tachinidae) or Europe” he made several changes to the names of Siphona spp., which have proved a bit confusing. The changes (and subsequent reversions) illustrate a few nice aspects of modern taxonomy and so I thought I would write a little piece on what happened.

Every species is based on what’s called a type specimen – ideally a specimen that the author considers to be the archetypal individual, which he uses to describe what the species looks like – a holotype. Later on if anyone wants to revise a group or they want to be absolutely sure of their identification they can hunt down the holotype and compare it to their own specimens, safe in the knowledge that the holotype is the definitive example of the species. In fact I have at times joked that the only ‘correctly’ identified specimen is the holotype – anything else is just an opinion!

When Andersen researched Siphona for his book he examined the types and noticed that actually what we had all been calling geniculata did not match the type specimen. When he examined all of the types he came to the conclusion that what we knew as geniculata should actually be called urbana and what we called cristata should be known as geniculata. This is not as unusual a situation as you might think because types are often hard to examine (being locked away in far-off museums) and people are fallible and they assume that they know what they are talking about!

Siphona geniculata and cristata are very common flies and it was quickly noticed that such a confusing change of names would cause massive problems for workers in the group. In 1999 Tschorsnig, Herting & O’Hara petitioned the International Commission on Zoological Nomenclature (ICZN, the body that defines the rules of naming and arbitrates on nomenclature in animals) and asked them to agree to redefine geniculata by reallocating a new type specimen to it. Their argument being that, although Andersen was strictly correct, the old names should be retained due to common usage. After much debate and time for reflection, in 2001 the ICZN voted on and decided to accept the suggestions.

The lectotype of geniculata was officially replaced by a new type specimen (neotype) held in the Museum of Lund University, labelled ‘Sk. Dalby, O. Molla, 21.VII.1989, leg. R. Danielson’. This action allowed cristata to be reinstated and we returned, full circle, to the situation prior to Anderson’s shake-up.

I always find this species-pair really difficult to split – even when you flip out the male genitalia. The cerci are actually quite distinctive but without good photos you can try to convince yourself that a rustica (the common one) is a tubulosa (the uncommon one). The key is that tubulosa should be really very parallel-sided while rustica is rounded and then the tip is quite pronounced.

Tachinid Times #26 has some very interesting articles on a few projects around the world to compile DNA phylogenies of tachinids. One such is by my good friend Jaakko Pohjoismäki, who is looking at European tachinids. He has a few genera and species that he is having trouble locating so I am listing them here in case anyone can help:

The specimens should preferably be collected in the 2000s, but as noted earlier we welcome also older samples. Dry and ethanol-preserved material are both acceptable. Ideally, we would like to borrow the whole specimen for documentation purposes. If you do not wish to donate the specimen, then it will be returned after sampling (removing a leg) and documenting together with a label, which helps to connect the specimen with the barcode in the future. Please feel free to contact us with your thoughts and suggestions. We’re hoping to hear from you!

The prosternum can be quite a difficult feature to find on a tachinid – partly because many British workers, used to Belshaw’s key will never have had to find it unless they have used the European or Palearctic keys. Here is a nice photo and the prosternum is the thin, dark, vertical strip of chitin in the middle of the picture, under the flies chin and between and slightly in front of the front coxae. Either side of it is a membranous area.

The keys nearly always ask whether the prosternum is hairy or bare – in the following photo the prosternum is bare but hairy examples have 1 or more fine, black hairs along the lateral edges.

Thelaira solivaga (male) showing the prosternum feature, which in this case is bare.

… and here is an example with a hairy prosternum – it is very difficult to see clearly but you should just be able to see small dark hairs towards the edge of the prosternum.

Exorista rustica (male) showing the prosternum, which in this case is hairy.

A combined image, zoomed in to show the hairs or lack of. Try to ignore the bristles on the coxae – under a microscope it is a little easier because you have a greater perception of 3-dimensions and the ability to move the specimen to the best orientation:

One of the big impediments to viewing the prosternum is usually poor pinning/mounting, which allows the head to drop or the front coxae to close together and block the prosternum from view. I have noticed this most often when specimens are pinned directly and dorsoventrally. If you pin a specimen laterally the head is less likely to drop down and if, in the rare event that it isn’t in a good position, you can easily manipulate it and use micro-pins to hold the specimen in position while it dries.

In my experience a lot of people have trouble with this genus because the traditional features used in keys are quite variable. In particular it is difficult to separate the common Thelaira nigripes from the rare solivaga.

All keys use the size of the outer-vertical bristles and the anterodorsal bristles on the middle tibia, which are a bit variable, and Belshaw (1993) uses the colour of the abdomen, which is one of the worst features to rely on – it is a confirmatory feature at best. This leads to a lot of Thelaira nigripes being wrongly classified as Thelaira solivaga – the 2 species are very similar but they can be distinguished if the correct features are used.

Belshaw is a little ambiguous when he talks of the middle leg only having “2 long bristles on its anterodorsal surface”. What constitutes “long”? All Thelaira have both long and short bristles on the ad surface of the mid tibia but I prefer to ignore the smaller ones at the top and bottom of the tibia and focus on the rest, in the middle. Here are some photos of Thelaira nigripes tibiae:

Here is a photo of a Thelaira solivaga mid tibia:

Also, a very useful approach is to look at the male genitalia – here is a nice set of figures from an article I saw a while ago:

Pay particular attention to the segment just before the genitalia themselves and the way that the surstylus curves. The distinction between nigripes and solivaga is still very fine but in conjunction with the other features you should be able to make a more confident determination. Later I will add some closeup photos of the male genitalia.